Table 1.

STRIVE Trial Strategies to Promote Participant Retention

Category	Description of Strategy	Considerations and Notes
Equipment	Cell phone/SIM card provided at enrollment	• At time of study planning, unclear whether most adults would own a cell phone.
Communications	Closed-user-group	• Participant could make free calls to trial hotline and study staff to report changes in health and request medical triage. • Free calls facilitated contact between participants and staff between scheduled monthly calls. • Study staff could make free calls to participants’ study cell phone in addition to personal telephone (multiple contacts).
Community engagement	Discussions with community leadership Leadership at local healthcare and Ebola facilities kept informed throughout the trial	• Ongoing community engagement to identify and address rumors. • Engagement of hospital leadership important for keeping participants engaged in study over time including returning for crossover vaccination.
Flexible appointments	Study staff worked in 2 shifts, which allowed calls and home visits to participants outside of working hours as needed	• Because participants were working at time of enrollment, they had to schedule appointments taking into account their work hours.
Multiple locator information	If participant could not be reached by telephone after 6 attempts, study staff attempted to reach them through relative telephone number or a home visit	• Multiple methods to track participants including study, personal and a relative's cell phone number, home address.
Staff training and feedback	Ongoing staff training to improve communication skills, confidentiality during home visits. Progress on percentage of persons due for follow-up reached discussed at weekly staff meetings	• Staff assigned to specific areas for tracking participants at home. Teams provided feedback on success of making all telephone calls; troubleshoot problems together.

Abbreviations: STRIVE, Sierra Leone Trial to Introduce a Vaccine Against Ebola.